A federal district court in New Jersey dealt a blow to Novartis division Sandoz’s efforts to invalidate two patents for Amgen’s inflammatory disorder treatment Enbrel (etanercept).

U.S. District Judge Claire Cecchi found Sandoz did not provide clear and convincing evidence to support claims that the two patents were deficient.

The Aug. 9 opinion is the latest in the battle over the Sandoz biosimilar Erelzi (etanercept-szzs). In 2016, Amgen filed suit against Sandoz for infringing on five of its patents in producing the biosimilar. In court, Sandoz admitted to infringement but disputed the validity of several of the patents.

The two patents at issue — originally filed by Hoffmann-La Roche and licensed to Amgen and its subsidiary Immunex — cover the active ingredient etanercept and methods to produce it. The federal court was not persuaded by Sandoz’s arguments that the patents were insufficiently written and based on prior art.